The influence of propranolol on catecholamine-induced changes in carbohydrate metabolism in the rabbit.

In vitro evidence has indicated that isoproterenol (ISO) is more potent than epinephrine (EPI) in releasing glucose from rabbit liver slices and that propranolol (PROP) is a competitive antagonist of ISO. In contrast, dose-response data from fasted rabbits have shown that EPI is more potent than ISO in increasing plasma glucose levels and in lowering hepatic glycogen levels. Pretreatment with PROP abolished ISO-induced hyperglycemia and changes in liver and muscle glycogen levels whereas only the muscle glycogen depleting effect of EPI was altered significantly. These results suggest that factors other than stimulation of hepatic beta-receptors must be involved in EPI-stimulated depletion of liver glycogen and hyperglycemia in the intact rabbit.